Trigger deploy on new CSB or brokerpak releases

[mogul]

Right now the brokerpak release version to be included is hard-coded in the app-setup.sh script. So to upgrade the version of the brokerpaks that are deployed, you have to edit the script to let it know about the new version.

Instead, this repository should poll for new releases in the upstream brokerpaks (or the CSB itself), then trigger a deploy if it sees one. (Or alternatively, generate a PR.)

The method for doing this is sketched out here: https://stackoverflow.com/a/58468828